Around 45 MPH, downhill with a tailwind! The trailers were single axle with dual wheels, one was a dry box for bottled beer, and the other was insulated for hauling iced-down kegs. I believe the maximum legal payload back then was around 16K pounds. The trailers had no brakes, and the tractors had mechanical brakes, later assisted by a vacuum booster on the brake pedal linkage.
A sheriff up in Kentucky used to watch one particularly steep hill, and any truck that had to use 1st. gear to climb it got weighed for a potential overload. One of the trucks pulled better than the other one, so the weak sister got a legal load and struggled up the hills. While that one was being weighed, the better hill-puller would sail by in 2nd. gear- - - - -with a big overload! They got away with that tactic for quite a while!
Jerry
